Media, for example fluids, can be heated by means of a thermal contact with materials having a positive temperature coefficient of electrical resistance (PTC materials). Hitherto, such PTC materials have been able to be shaped as disks or rectangular elements which consist of a single PTC material. Such disks or rectangular elements cannot be integrated at regions which are structurally difficult to access. As a result, short heating times and low heating powers cannot be realized since the disks or rectangular elements cannot be fitted where the heat is required.